1. Field of the Invention
The present invention relates to a reflection-type optoelectronic semiconductor device and, more particularly, to a reflection-type optoelectronic semiconductor device combining a reflecting face and an optical spectrum conversion layer.
2. Description of Related Art
Light emitting diodes (LED) can be divided into two types according to different structures: lens-type and reflection-type. In a lens-type LED, light from the LED chip is emitted from the light emission face. Contrarily, in a reflection-type LED, light from the LED chip is reflected by a concave reflecting face and then emitted.
Because light from a reflection-type LED is reflected by a concave reflecting face and then emitted from a light emission face, the light of the LED chip can be effectively emitted to the front. A reflection-type LED thus has a higher external emission efficiency than a lens-type LED.
From 1968, when the earliest LED was proposed, LEDs of many colors have been continually developed. After Nichia Corporation in Japan successfully developed a higher-efficiency blue LED in 1993, full-color LED products could then be realized. After blue LEDs were developed, white LEDs became the target pursued by the industry.
Today, the most mature commercial products are inorganic white LEDs developed by the Nichia Corporation (in the disclosure of U.S. Pat. No. 5,998,925 announced in Dec. 7, 1999 and in the disclosure of R.O.C. Pat. No. TW383508 announced in Mar. 1, 2000). FIG. 1 shows the structure of a lens-type inorganic white LED. The periphery of a blue LED chip 40 is filled with yellow light fluorescent powder 50. Light emitted by the blue LED chip 40 is used to excite the yellow light fluorescent powder 50 for producing a yellow light. At the same time, a blue light is also emitted. This blue light matched with the yellow light will form a blue-yellow mixed white light, which is finally scattered outwards by a lens.
In the lens-type inorganic white LED, however, after the light from the blue LED chip 40 is emitted, its optical path can't be effectively controlled. Therefore, the light may directly excite the yellow light fluorescent powder 50 or may be directly scattered outside so that mixing of the blue light and the yellow light can't be effectively accomplished, hence lowering the light emission efficiency.